leetcode 92 Reverse Linked List II
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode* reverseBetween(ListNode* head, int m, int n) { if(m==n) return head; int num=1; ListNode ln(0);ln.next=head; ListNode* pre=&ln,*cur=head; while(num<m&&cur) { pre=cur; cur=cur->next; ++num; } ListNode* npre=pre,*ncur=cur; while(num<=n&&cur) { ListNode* tmp=cur->next; cur->next=pre; pre=cur; cur=tmp; ++num; } npre->next=pre; ncur->next=cur; return ln.next; } };